1. Field of the Invention
The present invention relates to a liquid discharge head (ink jet head), a liquid discharge recording apparatus (ink jet recording apparatus), and a liquid discharge recording method (ink jet recording method) for performing recording by a liquid discharge recording system (ink jet recording system) in which liquid such as ink is discharged from discharge ports to form pixels on a print material and an image is formed by the pixels.
2. Related Background Art
As a copying machine, information processing equipment such as a word processor and a computer, and communication equipment become widespread, an image forming apparatus for those pieces of the equipment or the image forming apparatus which performs digital image recording as a single recording apparatus using a liquid discharge head rapidly becomes widespread. In the information processing equipment and the communication equipment, as quality of visual information is increased, and as the visual information is colorized, a high-quality image and colorization are also required for the recording apparatus.
In the recording apparatuses, recently the liquid discharge head in which nozzles including discharge ports of liquid such as ink (hereinafter simply referred to as ink) and liquid paths are integrated at high density is used in order to miniaturize an element according to the demand for the high-quality image. In order to perform the color recording, generally the recording apparatus includes ink heads which discharge the colors of the ink corresponding to, e.g., cyan, magenta, yellow, and black ink. Further, while the high-quality image can be formed, high-speed recording action is required for the recording apparatus. Therefore, in order to increase the number of pixels which can be formed at once to achieve the high-speed recording, the liquid discharge head tends to include a large number of nozzles.
Particularly a method, in which a length of the liquid discharge head is substantially set to a maximum width of a recorded print material to enable high-speed output by performing recording in one pass, is being realized. In this case, assuming that the A4 transverse feed page printer is used, the length of the liquid discharge head becomes about 30 cm. Assuming that nozzle density is set to 1,200 dpi (dot per inch), more than 14,000 nozzles are required by rough estimate. A large substrate is required in order to produce the liquid discharge head having such a large number of nozzles at once. Therefore, from the viewpoints of production cost and yield, it is very difficult to produce the liquid discharge head having a large number of nozzles.
Due to a large number of nozzles, it is difficult to produce all the nozzles so that the nozzles exert the same performance, and it is difficult that all the nozzles are maintained at constant performance. Therefore, it is thought that unevenness in ink discharge amount or a shift of landing spot is generated among the nozzles. In order to eliminate unevenness in optical density in the recording image, it is well known that a head shading correction technique is used.
A method of correcting the unevenness in optical density by measuring the optical density of the output image to perform feedback of the measurement result to input image data can generally be cited as an example of the head shading method. When the optical density is decreased because the discharge amount of a certain nozzle is decreased for any reason, evenness in the image optical density is achieved in the output image by performing the correction in which a gray-scale level is increased at a position corresponding to the nozzle.
Further, in a large number of nozzles, there is a possibility that the nozzle does not discharge the ink. In order to perform a complementation process against the problem that the nozzle does not discharge the ink, there is well known a not-discharge nozzle correction (not-discharge complementation) technique in which the image output can be performed even if not all the nozzles have no defect.
Examples of the not-discharge complementation technique include the method in which, when a certain nozzle does not discharge the ink, dots are formed at the positions adjacent to the dot (pixel) instead of the dot to be formed by the nozzle by using the nozzles located on the both sides of the nozzle, the method of performing the correction to the recording action image data so that the dot to be formed by the not-discharge nozzle is included in the surroundings (adjacent complementation), and the method of performing the correction by forming another color ink dot such as black at the position where the dot should be formed by, e.g., the not-discharge nozzle of cyan (different color complementation).